Old MSP RV-26 Police Globe - replacement bulb issue.

Hello!

Someone gave me an item from their retired collection to repair. It’s an old Michigan State Police Bulb Topper - you know, the red globe!

I cleaned it up and tested it out. I’m getting 12V as I should. I connected an LED strip to confirm that the bulb connections were working. They were. It was spinning and lighting up.

The replacement bulbs arrived that they purchased for me. Model 35PAR36SP5 from Bulb America. These are 35W/12V bulbs.

Something is off, though, when I connect one bulb and apply power, the bulb is really dim. Using my bench power supply, it’s wanting 12V at 4A.

If I connect the second bulb, the unit won’t lull more than 4A, and everything stops spinning and the bulbs are extremely dim.

If I increase voltage to 18V, they start to get brighter, but I know that’s not how they are designed.

Is this the totally wrong bulb or something?

I’m perplexed.

Thanks!!

 

[bpollard]

what are you using as a power supply? A 35 watt bulb needs about 3 amps @ 12 volts DC. (divide wattage/voltage to determine amperage).

Its sounds to me like either your power supply is inadequate, or your wiring is too small, or there is a high resistance (bad) connection somewhere. possibly in the brushes that contact the commutator in the rotating assembly.

your power supply needs to be able to supply close to 100 watts at 12 volts. to be on the safe side, I would call it 10 amps.

Perhaps also the motor has an issue, either mechanically or electrically, which is sucking up all the juice.

just my .02. there are others on this site that can probably give better advice

Bob

 

[KillerQ]

Hi!

I was giving it 12V with a bench power supply which provides as many amps as requested. It was only pulling 5A.

 

[dmathieu]

Not addressing the problem, but if you have a RV26, you need PAR 46 bulbs, not PAR 36 bulbs.

 

[bpollard]

Hi!

I was giving it 12V with a bench power supply which provides as many amps as requested. It was only pulling 5A.

Gotcha. I apologize if I am providing advice that you already know. If I were troubleshooting this, I might take the two new bulbs that you have out of the beacon. And wire them both up in parallel (Not in SERIES) with each other with at least 16 AWG wire and connect to the power supply on the bench. Both bulbs should pwer up as expected. If so, then there is something in the electrical circuitry of the beacon causing the issue.

If not, I would try another power source. even a 12 volt car battery

 

[stansdds]

First, are you certain that the motor is 12 VDC and not 24 VDC? Second, wiring should be parallel, not series as series wiring allows the first item in the series to draw the most current, potentially leaving little current for subsequent items in the series. Third, the correct bulbs for the Unity RV-26 are PAR-46 size sealed beam bulbs. Finally, if the the motor is confirmed to be 12 VDC, the bulbs are wired in parallel and the beacon spins slowly and/or the bulbs are dim, then your power supply may not be supplying sufficient amperage.

 

[KillerQ]

Not addressing the problem, but if you have a RV26, you need PAR 46 bulbs, not PAR 36.

Ah, thank you. They sent me the wrong ones. I will have them send me the correct ones and go from there.

First, are you certain that the motor is 12 VDC and not 24 VDC? Second, wiring should be parallel, not series as series wiring allows the first item in the series to draw the most current, potentially leaving little current for subsequent items in the series. Third, the correct bulbs for the Unity RV-26 are PAR-46 size sealed beam bulbs. Finally, if the the motor is confirmed to be 12 VDC, the bulbs are wired in parallel and the beacon spins slowly and/or the bulbs are dim, then your power supply may not be supplying sufficient amperage.

thanks. Yes, the motor is labeled with a sticker that says 12V DC which confirms that. As ware as series/parallel goes, it would spin slow with a dim bulb with only one light attached. I will try a different power supply, but I thought for sure that the bench supply would be best.

Another clue. When I attached a 12V 10A power pack, the entire unit would freeze until I disconnected it. I even co formed polarity. Odd.

With nothing attached, I confirmed that 12V is flowing by using a multimeter on one of the positive leads and the metal frame.

I’ll have to try a few more things and report back Tuesday.